1. Field of the Invention
The present invention relates to apparatus for separating recyclable plastic material from waste material, and in particular for separating and reclaiming certain plastic parts of film cartridges.
2. Description Relative to the Prior Art
It is generally known to separate materials based upon a difference in their specific gravity. U.S. Pat. No. 2,894,629 discloses a method for separating mixtures of divided solid materials comprising a heavy component and a light component. The solid material to be separated is fed to a tank containing a liquid having a specific gravity intermediate that of the light component and heavy component. The heavy component, therefore, sinks and can be recovered from the bottom of the container while the light component floats and can be recovered from the upper portion of the liquid. Such a method assumes the component parts of the material to be separated are physically divided as, for example, are coal particles which are to be separated from other mineral elements dispersed therein.
Examples are common, however, where the separation process is complicated by the fact that the component parts of the material to be separated are not physically divided and thus must be divided before attempting separation. U.S. Pat. No. 3,516,841 discloses apparatus for separating the metallic components from the plastic components in a metallic-plastic laminate structure. The metallic-plastic laminate structure is first chopped into relatively minute segments and then subjected to a shearing and grinding operation to further reduce the size of the segments and to free the metallic component from the plastic component. This metallic and plastic particulate mixture is fed to a separation tank (containing a liquid having a specific gravity in between that of the metal and plastic) wherein gentle agitation is provided to facilitate physical separation of the metallic and plastic components. The mixture then passes to a settling portion of the separation tank wherein the heavier component (usually the metallic component) sinks and the lighter component (usually the plastic component) floats.
Another method for separating components from a structure wherein the components are not originally physically divided is disclosed in U.S. Pat. No. 3,892,563. According to the disclosure, whole or shredded lead-acid batteries plus certain chemicals are fed into a rotating drum separator containing a plurality of grinding balls. Agitation of the mixture breaks up and degrades the battery fragments forming a heavy-medium suspension on which organic battery fragments (the battery case and the individual cell separators) float. The suspension constantly overflows from one end of the rotating drum thereby carrying the organic components to a trommel from which the organic components can be retrieved.
It is apparent that the method of separation of the components parts of a structure, material, article, etc. depends in large part upon the particular article to be separated. For example, the lead-acid battery separator described in U.S. Pat. No. 3,892,563 probably would not provide effective or efficient separation of components of a metallic-plastic laminate structure; nor would the metallic-plastic laminate structure separator disclosed in U.S. Pat. No. 3,516,841 be particularly suitable for the separation of components of a lead-acid battery. The present invention is directed towards the separation of the component parts of a film cartridge. The separation process depends in large part upon particular properties of the film cartridge itself.
Referring to FIG. 1, a super 8 movie film cartridge is shown comprising a polystyrene cartridge housing 10, a polycarbonate disc element 12, a butyrate roller post 14 and a brass leaf spring 16 which spring biases a polycarbonate pressure pad 18. Affixed by an adhesive to the cartridge housing 10 is a paper label 20. Polystyrene from the plastic housing 10 is reusable if it can be separated from the other components. Since the specific gravity of polystyrene is about 1.06 while the specific gravity of polycarbonate, butyrate and brass is about 1.25, 1.20 and 8.6 respectively, separation of the polystyrene component from the other components on the basis of differences in specific gravity seems to be an attractive approach. For example, one might break up the film cartridge to physically separate the various components and feed this mixture to a container holding a liquid with a specific gravity of about 1.1. The pieces of the polystyrene housing 10 should float while the remaining components sink, thereby allowing the polystyrene to be skimmed off the top of the liquid. However, there are several problems which stand in the way of such a technique. One of the problems is the labels. Being affixed to the plastic housing with an adhesive, the labels are not physically loosened from the housing by chopping up the film cartridge. Unless steps are taken to ensure otherwise, the labels remain affixed to the pieces of the plastic housing throughout the separation process thereby contaminating what would otherwise be recyclable polystyrene. Further, not only the labels themselves but also the adhesive used to bond the labels to the plastic housing must be removed. The general problem of removing labels and adhesive from plastic is recognized in "Processing the Plastics from Urban Refuse" by J. L. Holman et al., Bureau of Mines Solid Waste Research Program, Technical Progress Report 50, February, 1972, U.S. Department of the Interior, wherein it is stated "Labels, and the adhesives with which they are applied are difficult to remove, and remnants may be deleterious to subsequent use of the plastics . . . In table 5, the results of 1-hour scrubbing on samples . . . are shown in terms of the percentage of pieces still showing contamination". The "table 5" referred to indicates that after an hour of scrubbing about 5% of the pieces still have portions of labels or adhesive affixed thereto. Even though it is recognized that the removal of labels and adhesive from the plastic housing 10 is not easy, such removal must be accomplished effectively and at a reasonable cost if the polystyrene from the housing is to be reused. In this regard, it is known in the art to "laundry" cartridges by running them through a clothes-type washer in an effort to remove labels. It is further known to place the cartridges in an open vat of heated water. Although these methods have had varied degrees of success in removing labels from cartridges, most of them are very time consuming and expensive.